Mesoscale Precipitation Discussion 701
NWS Weather Prediction Center College Park MD
535 PM EDT Mon Aug 20 2018

Areas affected...Eastern AR...Northwest MS...Northeast LA

Concerning...Heavy rainfall...Flash flooding possible

Valid 202135Z - 210135Z

Summary...Additional heavy rain from repeated rounds of convection
is likely over saturated grounds, and this could cause additional
flooding early this evening.

Discussion...Regional Doppler radars and GOES-16 satellite imagery
have been showing an increase in shower and thunderstorm activity
over central and southern Arkansas ahead of a cold front.  The
convection is developing in response to increasing destabilization
in the boundary layer and diffluent flow aloft with PWs expected
to approach 2.2 inches per the latest RAP model analysis.  MLCAPE
is forecast to increase to near 3000 J/kg for the ArkLaMiss region
along with mid to upper 70s surface dew points.  Model forecast
soundings are suggesting deep layer unidirectional flow from the
west-southwest and this will support back-building convection and
therefore periods of very heavy rain with rates near 2 inches per
hour at times.

The latest suite of high res model guidance continues to depict
patchy areas of 1 to 2 inches of rain through 8:30 pm local time,
with isolated higher amounts possible.  An aggravating factor is
the extremely wet antecedent conditions and therefore very low FFG
values, particularly over the Mississippi Delta region where
several inches of rain has already fallen earlier today. 

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...

LAT...LON   35619053 35478992 35158950 34648933 34118943
            33568988 32989071 32729152 32689234 32769323
            33009381 33589368 34219306 35009196 35469130